long exposure recording

[mariom]

Hello, I just took a 45 minutes exposure on a mark III 1 Ds and it has more than 15 minutes rercording the image on the card and it has not finished. What is the normal

Time it should take the camera to record the image or is this normal?

[zml]

<p>If you have long exposure noise reduction set to on, the camera will take another exposure ("black frame") exposed for as long as the original frame and then "subtract" the sensor noise using that "black frame." It is in the manual, BTW.</p>

[mariom]

Still 1 hour and it hasn't recorded

[g dan mitchell]

<p>A 45 minute exposure with long exposure noise reduction enable will take 45 minutes for the exposure plus another 45 minutes for the "dark frame" exposure. This is normal. For exposures this long you DO want to have this setting enabled.</p>

<p>The "dark frame" captures a second exposure containing only non-photo data - e.g. the noise characteristics and hot pixels. It subtracts this from the original exposure to reduce these artifacts.</p>

<p>Dan</p>

[mariom]

<p>Thanks</p>

[mike_oflaherty]

<p>Hello, from what I have read you can turn off your NR on the camera and do it in post production using supplied software (DFP latest version). However this is only possiable if you are shooting RAW not JPG .</p>

[g dan mitchell]

<p>I don't think that the previous suggestion will work with long exposures, at least not based on my understanding of the specific issue with very long exposures.</p>

[kari v]

<p>You can't substract a dark frame without a dark frame. Long exposure NR is not normal NR.</p>